We’re being asked to calculate the mass of potassium bromide is contained in 35.8 mL of a potassium bromide solution that is 7.55% potassium bromide by mass and its density is 1.03 g/mL.

And to do that we're going to use the **mass percent formula** shown below:

$\overline{){\mathbf{mass}}{\mathbf{}}{\mathbf{percent}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{component}}{\mathbf{total}\mathbf{}\mathbf{mass}}{\mathbf{\times}}{\mathbf{100}}}$

Since we are dealing with a **solution**, we can rewrite the equation as:

$\overline{){\mathbf{\%}}{\mathbf{}}{\mathbf{mass}}{\mathbf{=}}\frac{\mathbf{mass}\mathbf{}\mathbf{solute}}{\mathbf{mass}\mathbf{}\mathbf{solution}}{\mathbf{\times}}{\mathbf{100}}}$

We don’t have the mass of the solution but we can calculate it using the **volume and density of the solution**.

**volume solution (density) → mass solution**

A potassium bromide solution is 7.55% potassium bromide by mass and its density is 1.03 g/mL. What mass of potassium bromide is contained in 35.8 mL of the solution?

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Based on our data, we think this problem is relevant for Professor Thyagarajan's class at JHU.